1. Field of the Invention
The invention relates to a manufacturing method for an electrode catalyst layer, a membrane electrode assembly and a fuel cell.
2. Description of the Related Art
Some of fuel cells use a membrane electrode assembly (MEA) in which electrode catalyst layers are respectively bonded to both surfaces of an electrolyte membrane. Each electrode catalyst layer includes a carrier, on which a catalyst is supported, and an electrolyte resin. Electrode reaction occurs at a so-called three-phase interface via the catalyst. At the three-phase interface, the passage of gas, the electrolyte resin and the carrier on which the catalyst is supported are in contact with one another. Therefore, the catalyst is desirably located at the three-phase interface. In addition, the electrolyte resin is desirably formed uniformly on the carrier.
For example, when vertically-aligned carbon nanotubes (hereinafter, also referred to as “vertically-aligned CNTs”) are used as a carrier, there has been suggested a technique that electrolytic solution in which electrolyte resin is dissolved in alcohol is dripped onto carbon nanotubes (hereinafter, also referred to as “CNTs”) and then dried to coat the surfaces of the CNTs with the electrolyte resin (see, for example, Japanese Patent Application Publication No. 2005-203332 (JP-A-2005-203332).
However, when the CNTs are long or when a distance between the adjacent CNTs is short, it is difficult for the electrolytic solution to penetrate into the back of a gap between the adjacent CNTs, so there is a possibility that the electrolyte resin cannot be formed uniformly on the surfaces of the CNTs.
Note that such a problem does not occur only when CNTs are used as a carrier, and also occurs, for example, when particles of carbon black, or the like, are used as a carrier.